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Hypoattenuation vs. FDG Avid

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Hypoattenuation vs. FDG Avid

Posted By
12/18/2019 10:53am
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Replies: 4

Need help understanding the difference in these terms. My husband, Larry , had a PET/CT scan in November which identified FDG avid spots in his spleen, deemed suspicious for metastatic disease. He had a follow up CT on Monday and the report now reads "unchanged hypoattenuating lesions in the spleen, which remain suspicious for metastatic disease, though treatment related sarcoidosis-like reaction is a consideration as well. Notably, these were FDG avid on PET/CT 11/4/2019." He has a clinic appt tomorrow and expect we'll find out - just want to have some education prior. Thanks.


Bubbles - (12/18/2019 - 4:19pm)

Hey Ann,

Basically, FDG is the stuff they inject into us during the scan. Cells that have high metabolic rates pick it up - in other words are "FDG avid". Cells that have high metabolic rates include cancer cells and our brains generally. BUT! Other cells are active and therefore pick up a lot of FDG as well, such as when they are affected by infection, inflammation, benign tumors or (as your radiologist mentioned) sarcoidosis - something we know that immunotherapy can cause. Here are some reports about that:

Hypoattenuating lesions - means that there are spots of LESS metabolic activity shown in those areas than in surrounding tissue.

Hopefully that will help with some of the nomenclature. Fingers crossed for good news tomorrow!!! Celeste

marta010 - (12/20/2019 - 11:13am)

Celeste - Thanks, as usual, for the very helpful information. We met with our local oncologist and also went to Mayo for a consult with the melanoma docs. Same conclusion from both teams - may or may not be metastatic disease, may or may not be immunologic side effect.. No way to conclusively know without doing invasive biopsy, which neither team was recommending. Ultimately, the treatment approach would be the same - resume full dose of Tafinlar (Larry's dose had been reduced from 3/4 to 1/2 when his scans were clear) and continue Keytruda. Re-assess after next quarterly PET/CT in Feb. If the spleen worsens or other progression occurs, plan A is to try to add MEK ( he was unable to tolerate this initially but given his lengthy (6+ years) tolerance of Tafinlar it might be a less complicated transition) or try one of the other BRAF combos. Plan B is IPI/Nivo if necessary. As usual, no magic bullet. Nonetheless, we left the appointment with a sense of relief and confidence that he will live to see another day:) On e day at a time is all you can more major milestone to look forward to with our son's wedding in May! Merry Christmas to you and your family - thanks for all you do for this community. Prayers for a happy and healthier 2020.
Ann & Larry

Bubbles - (12/20/2019 - 12:49pm)

Well, melanoma world never lets anything be simple does it, Ann??? Overall, if the "something or other" has to be there at all, sounds like you have a good plan in place!!! I hope you both have a lovely Christmas! And that wedding in May ~ WONDERFUL!!! Just got pics of my daughter's recent wedding in October up on the blog! That is a milestone to look forward to indeed! May your son's be as much crazy fun as hers was - if that's the way your peeps roll! HA! There is beauty in calmness and decorum, too. We just don't have a lot of that around here! HA! Either way - I wish you much joy. Celeste

Tracyyy - (12/27/2019 - 2:23pm)

Hi, we had similar experience. My mother is on a trial - spartalizumab - Taf/Mek since March 2018 for stage 3C unresectable. Since November 2018 her scans showed enlarged chest nodes wich where different on each scan and the oncologist thinks it might be sarcoidosis as she has excellent response on the primary site (inguinal lymph nodes). Now the chest nodes have almost disappeared but her PET scan showed uptake in her spleen and bone marrow associated again with inflamation as her next CT showed nothing there. So it is possible that your situaiton is the same. Good luck and May 2020 be better for all of us!